This is a phase I, open label, multiple dose, combination study of Nelfinavir, Zidovudine (ZDV), and Lamivudine (3TC). The combination will be administered to HIV infected pregnant women during pregnancy, labor and delivery, and postpartum and to their infants. Despite dramatic results of a 2/3 reduction of perinatal HIV transmission by administration of ZDV to mothers as reported in ACTG 016 trial, there is a need to develop new and more potent strategies to further reduce perinatal transmission. Data from several studies suggest that the prenatal treatment of the mother may be most important. ZDV is known to reduce the viral load on an average of 0.5 log, although this can vary between individuals. Combined antiretrovirals such as ZDV and 3TC can reduce virus load by 1.5 to 2 logs or triple combinations using protease inhibitors such as Nelfinavir can reduce viral load by > or equal to 2 logs and to below detectable levels. In a majority of subjects it is conceivable that initiation of treatment with triple combination during gestation may have the most potent effect on reduction of material virus load to its lowest, and in many cases, to undetectable levels prior to delivery. (ACTG 353, V. 2)